The disclosure of Japanese Patent Application No. 2001-186023 filed on Jun. 20, 2001, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The present invention relates to a variable intake device of an internal combustion engine and a method for manufacturing the device.
2. Description of Related Art
A variable intake device, in which the length of an intake tube and flow area are variable, has been developed to be used with internal combustion engines. With the internal combustion engine equipped with the variable intake device, high volumetric efficiency in a wide operation area can be secured by appropriately adjusting the cycle of the intake pulse through changes in the length of the intake tube or flow area.
A variable intake device for an internal combustion engine has been well known through a Japanese Utility Model Laid-Open Publication No. 63-156421. The variable intake device in the publication, as shown in FIG. 8, includes an intake controlling valve 51 in a surge tank 50 and adopts a system that changes the length of an intake tube 40 according to running status of the engine.
According to the variable intake device, the intake tube 40 is divided into two passages 52 and 53 by a partition wall 54 downstream from a throttle valve 60. The interior of the surge tank 50 is also divided into two chambers 55 and 56 which are connected to the passages 52 and 53 respectively. The intake tube 40 is further divided into each cylinder from both the chambers 55 and 56 through an intake manifold 61. An actual length of the intake tube is changed by communicating and interrupting communication between the chambers 55 and 56 as the intake controlling valve 51 opens and closes.
FIG. 9 shows a perspective view of the structure of a model resin surge tank provided at the variable intake device with an upper part 111 taken off. The resin surge tank includes an integrally installed structure equivalent to the intake controlling valve 51 and the passages 52 and 53 in addition to a structure equivalent to the surge tank 50 in the variable intake device shown in FIG. 8.
The surge tank mainly includes a surge tank body, which forms an outer wall of the surge tank 50, and a valve unit 110, at which the intake controlling valve 51 is provided.
The valve unit 110 mainly includes the intake throttle valve 51 and a structure for attaching the intake throttle valve 51. In the resin surge tank, the valve unit 110 is provided as an integral unit including a valve body 110A of the intake controlling valve 51, a frame 110B, an attachment flange 110C, and a driving device 110D. The attachment flange 110C is for fixing the valve unit 110 on the outer wall of the surge tank. The driving device 110D is for opening and closing the valve body 110A.
The surge tank body is divided into three parts: the upper part 111, a lower part 112, and a center part 113. The upper part mainly forms portions equivalent to an upper outer wall of the surge tank 50 and an upper outer wall of the passage 52 in FIG. 8. The lower part 112 mainly forms portions equivalent to a lower outer wall of the surge tank 50 and a lower outer wall of the passage 53 in FIG. 8. The center part 113 mainly forms portions equivalent to a side outer wall of the surge tank 50, side outer walls of the passages 52 and 53, and the partition wall 54 forming the passages 52 and 53 and both chambers 55 and 56 in FIG. 8.
Each connector for connecting a throttle body (not shown), which is provided with the intake manifold 61 and the throttle valve 60, to the resin surge tank is formed at the center part 113. A partition wall 113A (equivalent to the partition wall 54 in FIG. 8) for dividing the interior of the surge tank 50 into two chambers is also formed at the center part 113. An opening of the partition wall 113B, into which the valve unit 110 is installed, is formed at the partition wall 113A. Furthermore, an attachment flange 113C for fixing the valve unit 110 is provided at the center part 113.
Each part (111, 112, and 113) is formed from resin. Many of the parts (the frame 110B, for example) of the valve unit 110 are also formed from resin.
The above-described resin surge tank is manufactured through the following three steps:
(1) fixing each part together through welding to integrally assemble the surge tank;
(2) installing the valve unit 110 into the opening of the partition wall 113B; and
(3) tightening the attachment flanges 110 and 113 together with a bolt 114 to fix the valve unit 110 to the center part 113.
Because of the attachment structure of the above-described valve unit 110, a clearance is formed to a certain extent between the outer margins of the frame 110B and the opening of the partition wall 113B or between both the attachment flanges 110C and 113C. To obviate the above-mentioned problem, gaskets 115 and 116, which are formed from an elastic body such as rubber, are inserted into the clearance of the resin surge tank according to the present invention to secure sealing performance necessary for the resin surge tank.
The above-described variable intake device can be manufactured at low cost by forming the surge tank, in which the intake controlling valve 51 is housed from resin as described above. However, as described below, a variable intake device adopting the above-described attachment structure of the valve unit 110 has problems which must be addressed and resolved in order to further improvement of its productivity and intake performance.
The valve unit 110 of the resin surge tank is fixed to the attachment flange 110C of the valve unit 110 and to the attachment flange 113C of the center part 113 sufficiently. However, the outer margins of the frame 110B and the opening of the partition wall 113B are not completely fixed together since they are just connected through the gasket 116. Therefore, the valve unit 110 is attached to the center part 113 as a cantilever supported by the attachment flange 110C. Further, vibration from the frame 110B may be generated as an internal combustion engine vibrates. As a result, a size of the valve body 110A is restricted to avoid fatigue break of the valve unit 110 due to the vibration. Furthermore, restrictions such as the need for increasing the width and thickness of the frame 110B are also considered in designing the variable intake device. Therefore, the restrictions become obstacles to securing intake performance and lightening the resin surge tank.
The present invention has been developed in consideration of the above-mentioned problems and its object is to allow a variable intake device with a resin surge tank, in which an intake controlling valve is housed, to be manufactured more appropriately.
The following describes means to achieve the above-mentioned object and action effects of the means.
A variable intake device for an internal combustion engine according to an aspect of the present invention includes a resin surge tank including a plurality of chambers divided by a partition wall and an opening of an outer wall and a valve unit including a control valve that selectively opens and closes to communicate and interrupt between the chambers by opening and closing the partition wall and a resin frame forming a peripheral frame of the control valve, wherein the valve unit is fixed at the opening of the outer wall and integrally fixed at least at a portion of a plurality of contact portions between an opening of the partition wall and the resin frame.
A method for manufacturing the variable intake device includes the following two steps. First, a valve unit, which includes a control valve for communicating and interrupting between chambers by opening and closing a partition wall and a resin frame forming a peripheral frame of the control valve, is inserted into an opening of the outer wall of a resin surge tank, which includes the plurality of chambers divided by the partition wall and the opening of the outer wall, in order to install the periphery of the resin frame into the opening of the partition wall in the resin surge tank. Next, the laser beam for welding is radiated through a portion, at least a portion of which is formed from resin material which transmits light from a laser beam, to weld contact faces between the resin frame and the opening of the partition wall through the laser welding.